Augmented-reality display systems overlay a computer-generated or electronically controlled image on an observer's view of the real world. Examples of such display systems include heads-up displays, often referred to as HUDs. Generally, a heads-up display is any transparent display that presents data without requiring users to look away from their usual viewpoints. HUDs are now used in military and commercial aircraft, automobiles, and other professional applications. Augmented-reality displays are also mounted into head-worn devices and referred to as head-mounted displays or helmet-mounted displays (HMDs). Such head-mounted augmented reality displays should be small and light-weight and should not obscure a user's view of the real world.
Most HUDs or HMDs use an optical projection system with a transparent screen in the user's field of view, for example as described in U.S. Pat. No. 3,709,589. Such an arrangement provides excellent transparency but can require complex optics and is relatively bulky. A more recent augmented-reality system discussed in U.S. Pat. No. 9,632,315 mounts an optical projection system into a pair of spectacles. However, in any augmented-reality display system, there is a need for visually integrating the augmented-reality display into the user's field of view as naturally and seamlessly as possible.
In some applications, the periphery of the HUD or HMD is clearly defined, for example when integrated into a pair of spectacles or a partially opaque helmet. In other applications, the display is integrated into a wider visual field in a viewing environment. There is a need, therefore, for transparent displays that are thin and transparent and are aesthetically and visually integrated into a user's field of view.